1. Technical Field of the Invention
This invention relates generally to radio receivers and more particularly to reducing receiver interference.
2. Description of Related Art
As is known, the general architecture of a radio includes a radio receiver and a processor. The radio receiver receives a radio frequency (RF) signal and converts it into a baseband signal. The processor recovers embedded data of the RF signal from the baseband signal.
To manufacture a commercially viable radio, the radio receiver should be designed to mitigate the adverse affects of interfering signals external to the radio (e.g., adjacent channel interference) and to mitigate the adverse affects of interference from within the radio. To reduce adjacent channel interference, the bandwidth of the radio receiver is relatively narrow such that signals outside of a frequency band of interest (i.e., adjacent channels) are substantially attenuated while signals within the frequency band of interest (i.e., the desired channel) are not attenuated. In addition, radio receivers include a plurality of techniques to reduce internal interference. For instance, radio receivers utilize component matching, synchronization, calibration, temperature compensation, etc.
One internal source of potential interference that has not been addressed is harmonics of the switching rate of a switch mode power supply falling within the frequency band of interest. In some applications, this is not an issue since the frequency band of interest is significantly greater than the switching frequency such that the harmonics that may fall within the frequency band of interest are of negligible magnitude and/or because the switch mode power supply is physically, and thus, electromagnetically isolated from the radio receiver (e.g., the power supply is implemented on a different integrated circuit than the radio receiver). However, as the frequency of switch mode power supplies increase and/or as integration of the switch mode power supply and radio receiver occurs, the harmonics of the switching rate of the switch mode power supply may adversely affect the performance of the radio receiver.
Therefore, a need exists for a method and apparatus to mitigate interference from a switch-mode power supply.